1. Field of the Invention
The present invention relates to a capping apparatus and a recovering apparatus for an ink jet head, and an ink jet printer having the ink jet head.
2. Description of the Related Art
Conventional recovery apparatus for the ink jet head of the ink jet printer includes an apparatus for protecting the jet nozzle of an ink jet head and/or preventing the nozzle from drying. This apparatus includes a cap for covering the jet surface in such a manner that the cap can open and close the surface. Another conventional recovery apparatus is a suction apparatus for sucking and discarding the thickened ink in an ink jet head so as to prevent the jet nozzle from being clogged or remove clogging ink, if any, and/or for introducing ink into the head when the ink cartridge is replaced. The suction apparatus includes the cap and a pump connected to the suction cavity or recess of the cap.
The front surface of the cap of such a recovery apparatus is brought into close contact with the jet surface and separated from it in a state that both the surfaces are in parallel each other. Therefore, when the surfaces contact closely together, the air in the cap cavity is pressurized, pushing back the meniscus in the nozzle, so that air may be entrained. When the surfaces separate from each other, particularly in the case of a suction apparatus, air is entrained due to the residual negative pressure because the whole cap surface is separated at a time from the jet surface. This may cause splash or scatter of ink, and may also entrain air bubbles into the nozzle, preventing ink from being jetted.
FIG. 5 shows a conventional recovery apparatus including a cap 30 fixed to a support 34, which is biased by a spring 31 so as to normally incline the cap 30. The inclined cap 30 can be gradually brought into close contact with the jet surface 32, and gradually separated from it. Apparatus of this type are disclosed in, for example, Japanese Patent Applications Laid-Open No. 3-93548, No. 7-68788, and No. 7-68766 corresponding to GB 2,269,344.
The cap 30 of the apparatus shown in FIG. 5 can turn around a horizontal pin 33, which is positioned at the support 34 opposite the front surface 30a of the cap. Consequently, when the cap 30 turns after the lower portion of the cap brim 30b contacts with the jet surface 32, this lower portion shifts or slips down from the position where it first contacts. It is therefore necessary to make the jet surface 32 large enough for accommodation to the slip of the cap 30. This may increase the size and/or costs of the apparatus. In addition, the foregoing cap motion occurs frequently, and the cap 30 slips each time the motion occurs. As a result, the cap brim 30b may deform, decreasing the closeness of contact of the cap 30.
The recovery apparatus shown in FIG. 5 is fitted to the ink jet printer separately from the ink jet head. As a result, the cap surface has a slight inclination relative to the jet surface due to inaccuracy of parts, fitting inaccuracy, and the like. Therefore, in order to securely prevent air from being entrained as stated above, it is necessary for the cap to have a large inclination to some extent. If the cap has a large inclination, however, the lower contact portion of the cap brim slips more. This may make the foregoing problem more serious.
The conventional recovery apparatus has another problem as stated below.
Before the ink jet printer starts printing, the recovery apparatus purges the inside of the nozzle through its purge chamber by means of a pump. Then, while the cap is released with, for example, its top being opened, the pump sucks further to purge away the ink which has been sucked from the nozzle toward the purge chamber and has adhered to the jet surface. As a result, it is possible to prevent the nozzle from being clogged with ink or remove clogging ink. It is therefore possible to suck and discard the thickened ink, and/or introduce ink into the ink jet head when the ink cartridge is replaced. If the cap was separated from the nozzle with the cap surface in parallel to the jet surface, excessive negative pressure would develop in the purge chamber. The entrainment of air due to the negative pressure would splash or scatter ink, and/or mix air bubbles with the ink in the nozzle. Therefore, when the cap is released, the cap is inclined in such a manner that it is opened from above. Such technique is disclosed in Japanese Patent Application Laid-Open No. 3-93548 etc.
When air is sucked while the cap of the conventional recovery apparatus is released, at least the lowest jet ports in the jet surface contact with the ink remaining in the purge chamber until the air suction ends. As a result, until the air suction ends, ink is entrained and flows back together with air bubbles into the nozzle, through the jet ports in contact with the ink, due to the ink turbulence and/or air turbulence occurring when the cap is released.
In greater detail, as shown in FIG. 9, the cap 214 has a suction port 214b formed through it above the lowest jet ports 211a of the jet head 211. Specifically, as shown in the upper half of FIG. 9, the distance "a" between the top of the suction port 214b and the bottom of the cap brim 214a is longer than the distance "b" between the bottom of each lowest jet port 211a and the bottom of the brim 214a (a&gt;b). As a result, until the air suction with the cap 214 and jet head 211 ends, ink 100 is entrained and flows back with air bubbles into jet ports 211a due to the ink turbulence and/or air turbulence occurring when the cap 214 is released.
The ink which has flowed back and contains air bubbles and/or the like may cause defective jet when printing starts. As a result, the recovery by suction is less effective, so that the print may be defective. It is therefore not possible to meet general demands for recent high-quality printing in the technical field of ink jet heads.